Immunological, biochemical and morphological studies are proposed to identify cell surface constituents specific to purified populations of mouse spermatogenic cells, from primitive type A spermatogonia to mature spermatozoa. A number of antibodies, having different immunological specificities, have already been prepared and their binding properties to mouse spermatogenic cells have been analyzed. Current studies involve the preparation of plasma membrane fractions from isolated mouse spermatogenic cells using two procedures. One method involves hypotonic lysis followed by isopycnic density gradient centrifugation. The other technique involves the binding of intact cells to poly-l-lysine coated acrylamide beads followed by mechanical shear. Purified plasma membrane fractions should allow the biochemical analysis of particular antigenic moieties by immunocoprecipitation and polyacrylamide gel electrophoresis in two dimensions. Radio-labeling techniques specific for cell surface components are being investigated in order to increase the sensitivity and resolution of the biochemical studies. These experiments will facilitate the production of monospecific antisera, which when used in conjunction with detailed biochemical data regarding individual antigens, should enable functional assays to the role of the plasma membrane in the regulation of mammalian spermatogenesis.